zài / gǔdài / shūxìn / zhōng / niánqīng / de / dúshūrén / yǒushí / chēng / niánzhǎng / de / tóngmén / wéi / yàn / xiōng

在古代书信中，年轻的读书人有时称年长的同门为砚兄。

In ancient letters, younger scholars sometimes addressed an older fellow student as yànxiong.